Device for welding molded plastic parts permitting simultaneous and mutually independent welding processes

ABSTRACT

An apparatus for simultaneously welding multiple molded plastic parts includes a power delivery module, a measuring arrangement, a parameter storage module, a user interface, and a controller, is designed for use with plastic parts that each have at least one fitting with a heating element and an identifying resistor. The power delivery module is designed to supply power to the multiple heating elements and includes a common power supply, multiple independently controllable power switching devices and multiple outputs, each designed for interconnection with one of the fittings. The measuring arrangement includes multiple interconnections for connecting to the heating element and identifying resistor of each fitting to which an output is connected. The measuring arrangement measures the resistance of the heating element and the identifying resistor of each fitting connected to the apparatus. The parameter storage module stores the power output level and power duration parameters for fittings of different types based on the resistance values of their heating elements and identifying resistors. The controller is connected to the user interface, the parameter storage module, the power delivery module, and the measuring arrangement. The controller operates to perform the following functions: cause the measuring arrangement to measure the resistance of the heating element and identifying resistor of each fitting; access the parameter storage module to identify the power output level and power duration parameters for each fitting; and cause the power delivery module to simultaneously deliver power to each of the outputs connected to the fittings and control the power switching devices so that power is supplied to each of the outputs for the duration and at the level identified for the fitting connected to the output.

FIELD OF THE INVENTION

The present invention relates to a device for welding molded parts, madeof plastic.

BACKGROUND OF THE INVENTION

In order to connect tubular molded parts made of a synthetic material,welding sleeves are used as a rule. These sleeves have a heatingelement. By supplying electrical heating energy the heating element isheated and the sleeve is welded with the tubular molded part. In thisway, a wide variety of molded parts in pipeline systems are connectedtogether. The energy necessary for the welding process is supplied froma welding device. These devices are designed such that a variety ofwelding programs are stored for different molded parts and release theenergy respectively required for the molded part to be welded. Theenergy required depends on the material, the type and the size of themolded part. The required welding time is also controlled by the moldedpart parameters. For example, the welding time required during thewelding of pipes, while using a heater coil welding sleeve with anominal diameter of 63 mm amounts to approximately 2 min. In the case oflarger pipe dimensions, the welding time increases correspondingly.During this time, no additional welding with the welding device can takeplace. However, on the construction site, a multitude of such weldingsmust often be carried out simultaneously. Since the welding operationsmust take place in succession, this process requires a great deal oftime.

The known welding devices are designed in such a way that in the case ofnew molded parts, the changed parameters, for example, dimension ormaterial, which require changed welding parameters, can no longer beprogrammed into the welding device at a later time. For this reason,different welding devices are required for different molded partcategories.

SUMMARY OF THE INVENTION

It is an object of the present invention to create a device for weldingmolded parts with which the welding process can be carried out onseveral different molded parts simultaneously.

In accordance with the invention, this problem is solved by means of adevice for automatically and simultaneously welding multiple moldedplastic parts.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is explained in greater detailby means of the enclosed figures, wherein

FIG. 1 shows a device of the invention;

FIG. 2 shows the device from FIG. 1 with three different molded partsconnected,

FIG. 3 is a diagram showing components of the invention; and

FIG. 4 is a cross sectional view of a fitting taken along lines 4--4 ofFIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a welding device for joining molded parts made of plastic.The device has a housing (1) which consists essentially of two plasticshells and which surrounds and protects the functional units and theelectronics of the device. In order to facilitate transportation,particularly at construction sites, a handle (2) is provided. Among thefunctional units of the welding device, in particular a supply unit anda control unit are included. The supply unit includes a line connection(3), a transformer and three output terminals (4) for connecting thewelding cables (15). The energy supply to the molded parts to be weldedtakes place via the output terminals (4) and the welding cables (15).Several output terminals (4) with corresponding welding cables (15) maybe provided.

The control unit has a processing arrangement 21 and a measuringarrangement. The measuring arrangement 22 serves for identifying amolded part connected to the welding device via a welding cable (15).This takes place by measuring a resistor 20a-20e arranged on the moldedpart. On the basis of the resistance value, the processing unit 21recognizes the welding parameters and adjusts to the necessary weldingcurrent, as well as the required welding time. With these weldingparameters, the energy supply can be controlled simultaneously atseveral different molded parts. This welding process is the reason forrecognition and control of welding channels.

In the processing arrangement, all welding data of the commonlyavailable molded parts are stored. A printed circuit board includes theprocessor and measuring circuits, the operating and indicator elementsand the memory card plug 12. Via an interface (12) at the housing, thememory card 23, on which the welding parameters of a new molded part arestored, can be read in. This data can be read in via the processor unit21 and are stored there.

At the front surface of the housing, the operating elements, such as astart button (6) as well as different display elements are arranged. Thedisplay elements (7, 8 and 9) indicate the operating states of a weldingprocess: Ready, Welding and Finished. A display (10), which indicateswhether the respective energy supply channel is in the welding process,is assigned to each welding channel. Display (11) indicates disruptionsduring a welding process.

FIG. 2 shows one application of the welding device. The welding deviceis connected at the line connection (3) by means of a line cable (13)via an outlet (14). Three different molded parts (16, 17 and 18) areconnected to the welding device by welding cable (15). Molded part (16)is a T-piece with three branches each branch having a welding zone.Molded part (17) is a transition piece and molded part (18) is a heatingcoil welding sleeve with a large nominal diameter. All molded parts (16to 18) have a predetermined resistor which is secured on a board withinthe molded part. The fitting resistance is the resistance of the heatingcoil 24. The identification of the fitting takes place via the measuredproduct resistance and the heating coil resistance. These arerecognizable by the processor unit.

The welding parameters belonging to a fitting are the welding currentand the welding time.

In order to bring about a welding process, the user must operate thestart button (6). The welding process is started. The welding deviceidentifies and controls all connected energy supply channelssimultaneously. Each connected molded part (16 to 18) is welded with theprogrammed current during the programmed time with a tubular element.The display lights (10) of the individual energy supply channels turnoff as soon as the welding process has been successfully completed. Thedisplay (9) lights up as soon as the welding process with the longestwelding time is ended and indicates that the welding device is ready forsubsequent welding processes.

With the described welding device, it is possible to carry out severalweldings with the same or a different welding energy. Since all energysupply channels are mutually independent, it is possible to undertakeonly one or two weldings simultaneously.

The advantage of the described invention lies in that several weldings,in which the welding parameters may vary, can be carried outsimultaneously. This is time-saving and economical.

Moreover, later changes or expansions of the molded part supply, whichlead to new welding parameters, can be read into the device of theinvention at any time by means of a memory card.

We claim:
 1. An apparatus for simultaneous and mutually independentlythermally welding a plurality of molded plastic parts, each of theplastic parts having at least one fitting with a heating element and anidentifying resistor, the heating element operative to heat the fittingwhen power is supplied to the fitting, the apparatus comprising:a powerdelivery module for supplying power to the heating elements, said powerdelivery module having a common power supply, a plurality ofindependently controllable power switching devices connected to saidpower supply, and a plurality of outputs each adapted forinterconnection with one of the fittings, one output connected to eachof said plurality of switching devices, each switching device beingoperative to control the duration and power level of power supplied tothe connected fitting; a measuring arrangement having a plurality ofinterconnections for connecting to the heating element and identifyingresistor of each fitting to which an output is connected, said measuringarrangement being operative to measure the resistance of the heatingelement and identifying resistor of each connected fitting; a parameterstorage module for storing power output level and power durationparameters for fittings of different types based on resistance values ofheating elements and identifying resistors; a user interface having aninitiation means for activating the welding apparatus; and a controlleroperatively connected to said user interface, said parameter storagemodule, said power delivery module, and said measuring arrangement, saidcontroller operative to perform the following functionsa) cause saidmeasuring arrangement to measure the resistance of the heating elementand identifying resistor of each fitting connected to saidinterconnections; b) access said parameter storage module to identifythe power output level and power duration parameters for each fittingconnected to said interconnections; c) cause said power delivery moduleto simultaneously deliver power to each of the outputs connected tofittings when said initiation means is activated, and control said powerswitching devices so that power is supplied to each of the outputs forthe duration and at the level identified for the fitting connected tothe output.
 2. A method of simultaneously and mutually independentlythermally welding a plurality of plastic parts, said method comprisingthe steps of:a) providing a plurality of fittings, each fitting having aheating element and an identifying resistor, b) measuring the resistanceof the identifying resistor and the heating element of each of theplurality of fittings; c) choosing an output power level and duration ofpower output for each fitting based on the resistances measured in stepb); d) simultaneously and independently supplying power to the heatingelements in each of the plurality of fittings at the output power leveland for the duration chosen for each fitting.